High performance re-entry vehicles and interceptor missiles will experience heating under conditions that challenge the ablation and/or insulation capabilities of conventional thermal protection materials applied thereto. These conditions include short-term exposure of the thermal protection materials, during ballistic ascent or re-entry through the atmosphere, to very high temperatures which will ablate any known material. These conditions also include long-term exposure to relatively lower heat flux levels, while gliding in the atmosphere, which can produce elevated temperatures deep inside the thermal protection material, thereby diminishing its insulative properties.
Typically, thermal protection materials employed for high performance ballistic re-entry (e.g., tape wrapped carbon phenolic and silica phenolic fabric composites) perform well under ablation but have insulation capabilities that are not sufficient to protect against overheating after long periods of thermal soak unless an excessive mass of insulating material is utilized.
Previously, the insulation capability of high density composite fabric ablative layers has been improved by superimposing and bonding a plurality of such layers by use of adhesives, stitching, and/or reinforcing elements or fasteners. However, the weight of high density ablative outer layers, needed to provide sufficient insulation, has typically been excessive, thereby resulting in reduced mission range and/or payload to accommodate this added weight.
Alternately, low density, lightweight resin foam or honeycomb have been used as an inner insulating layer, which is laminated to an outer composite fabric heat shield layer, by resin bonding, to provide suitable ablative and insulative protection at lower weights. However, many of these laminates have experienced delamination under adverse thermal conditions as could be experienced during the flight profile.
Therefore, a need exists for an ablative/insulative composite, having sufficient thermal protection capabilities, wherein the composite is lighter weight and will not fail (e.g., delaminate) during use.